The present invention relates generally to lithography systems. More particularly, the present invention is directed to determining spatial relationships between an imprinting mold and a substrate upon which a pattern will be formed using the imprinting mold.
Imprint lithography has shown promising results in fabrication of patterns having feature sizes smaller than 50 nm. As a result, many prior art imprint lithography techniques have been advocated. U.S. Pat. No. 6,334,960 to Willson et al. discloses an exemplary lithography imprint technique that includes providing a substrate having a transfer layer. The transfer layer is covered with a polymerizable fluid composition. A mold makes mechanical contact with the polymerizable fluid. The mold includes a relief structure, and the polymerizable fluid composition fills the relief structure. The polymerizable fluid composition is then subjected to conditions to solidify and to polymerize the same, forming a solidified polymeric material on the transfer layer that contains a relief structure complimentary to that of the mold. The mold is then separated from the solid polymeric material such that a replica of the relief structure in the mold is formed in the solidified polymeric material. The transfer layer and the solidified polymeric material are subjected to an environment to selectively etch the transfer layer relative to the solidified polymeric material to form a relief image in the transfer layer.
U.S. Pat. No. 5,772,905 to Chou discloses a lithographic method and apparatus for creating patterns in a thin film coated on a substrate in which a mold, having at least one protruding feature is pressed into a thin film carried on a substrate. The protruding feature, in the mold creates a recess in the thin film. The mold is removed from the thin film. The thin film then is processed such that the thin film in the recess is removed exposing the underlying substrate. Thus, patterns in the mold are replaced in the thin film, completing the lithography process. The patterns in the thin film will be, in subsequent processes, reproduced in the substrate or in another material which is added onto the substrate.
Yet another imprint lithography technique is disclosed by Chou et al. in Ultrafast and Direct Imprint of Nanostructures in Silicon, Nature, Col. 417, pp. 835-837, June 2002, which is referred to as a laser assisted direct imprinting (LADI) process. In this process a region of a substrate is made flowable, e.g., liquefied, by heating the region with the laser. After the region has reached a desired viscosity, a mold, having a pattern thereon, is placed in contact with the region. The flowable region conforms to the profile of the pattern and is then cooled, solidifying the pattern into the substrate.
An important consideration when forming patterns in this manner is to maintain control of the distance and the orientation between the substrate and the mold that contains the pattern to be recorded on the substrate. Otherwise, undesired film and pattern anomalies may occur.
There is a need, therefore, for accurately determining spatial relationships between a mold and a substrate upon which the mold will form a pattern using imprinting lithographic processes.